1. Field of the Invention
The present invention relates to a micro lens array provided with a thin film, a method of manufacturing the same, and a display device.
2. Description of Related Art
A micro lens array formed by lining up plural micro-sized lenses have been applied to liquid crystal panels and the like. Each lens of the micro lens array converges incident light upon each pixel to illuminate a display screen.
As a method of manufacturing a micro lens array, a method using dry etching or wet etching has been known. However, such a method requires a step of lithography for an individual micro lens array, thereby increasing production costs.
Because of this, a method of manufacturing a micro lens array which comprises dripping a liquid resin onto a master mold having spherical surfaces corresponding to lenses formed thereon, solidifying and removing the resin has been developed as disclosed in Japanese Patent Application Laid-Open No. 3-198003.
In this method, lithography for each product is not needed since a micro lens array is formed by utilizing the master mold. Since the master mold can be repeatedly used as long as durability permits, the percentage of the cost of the master mold in one product decreases as the durability of the master mold increases, leading to a reduced product cost.
A micro lens array for a liquid crystal panel is then provided with a thin film. An ITO (Indium Tin Oxide) film, which is an example of the thin film, is manufactured by forming a film under vacuum by a method such as sputtering or vapor deposition and then annealing the film. The annealing temperature is usually 200 to 300xc2x0 C., and higher temperature is preferable to reduce resistance and to form a high quality electrode film.
However, such high-temperature annealing not only adversely affects the micro lens array but also limits the materials available for the micro lens array. A micro lens array for a liquid panel is provided with an alignment layer. The alignment layer aligns liquid crystal molecules and has to be flat. The alignment layer is formed by, for example, applying a polyimide resin and baking the resin. However, heat used for baking not only adversely affects the micro lens array but also limits the materials forming the micro lens array. As described above, conventional methods have various problems in manufacturing the thin film.
The present invention has been achieved to solve the above problems. An objective of the present invention is to provide a method of manufacturing a micro lens array having a thin film at low cost, a micro lens array produced by this process, and a display device using the micro lens array.
(1) A method of manufacturing a micro lens array according to the present invention comprises a first step of forming a thin film on a base, a second step of forming a light-transmitting layer having a plurality of lenses on the thin film, and a third step of removing the thin film together with the light transmitting layer from the base.
According to the present invention, the thin film is formed and then annealed. After that the light-transmitting layer is formed on the thin film. Since the light-transmitting layer has not yet been formed when the thin film is annealed, the light-transmitting layer is not affected by high temperature annealing. In addition, since the materials for the light-transmitting layer are not limited to the materials which can withstand high temperature annealing, the range of choice for materials is widened.
(2) In the method of manufacturing a micro lens array, the thin film may be a transparent electrode film.
In this method, the transparent electrode film is formed and then annealed. After that the light-transmitting layer is formed on the transparent electrode film. Since the light-transmitting layer has not yet been formed when the transparent electrode film is annealed, the light-transmitting layer is not affected by high temperature annealing. In addition, since the materials for the light-transmitting layer are not limited to the materials which can withstand high temperature annealing, the range of choice for materials is widened.
(3) The method of manufacturing a micro lens array may further comprise a step of forming the light-transmitting layer separately from the thin film before the second step, and the light-transmitting Layer may be adhered to the thin film in the second step.
This method is general-purpose since it is possible to utilize a light-transmitting layer having lenses prepared in advance.
(4) In the method of manufacturing a micro lens array, the light-transmitting layer may be adhered to the thin film while forming the light-transmitting layer from a light-transmitting layer precursor on the base in the second step.
This method can reduce the total number of steps since the thin film and the light-transmitting layer are continuously formed.
(5) In the method of manufacturing a micro lens array, the base may have radiation transmissivity, and the thin film may be exposed to radiation through the base to reduce the bonding force at the interface between the thin film and the base in the third step.
The thin film can be easily removed from the base by reducing the bonding force at the interface between the thin film and the base.
(6) In the method of manufacturing a micro lens array, a separation layer may be previously formed on the base and the thin film may be formed on the separation layer in the first step. The base may have radiation transmissivity, and the separation layer may be exposed to radiation through the base to reduce the bonding force at the interface between the base and the separation layer in the third step.
In this manner, the bonding force at the interface between the base and the separation layer is reduced, whereby the separation layer can be removed from the base.
(7) In the method of manufacturing a micro lens array, a separation layer may be previously formed on the base and the thin film may be formed on the separation layer in the first step. The base may have radiation transmissivity, and the separation layer may be exposed to radiation through the base to reduce the bonding force at the interface between the thin film and the separation layer in the third step.
The bonding force at the interface between the thin film and the separation layer is thus reduced, whereby the thin film can be removed from the separation layer.
(8) In the method of manufacturing a micro lens array, a separation layer may be previously formed on the base and the thin film may be formed on the separation layer in the first step. The base may have radiation transmissivity, and the separation layer may be exposed to radiation through the base to reduce the bonding force in the separation layer in the third step.
Reduction of the bonding force in the separation layer causes removal (or cohesion failure) in the separation layer. In this case, part of the separation layer adheres to the micro lens array and the remainder adheres to the base.
(9) The method of manufacturing a micro lens array may further comprise a step of washing the surface of the thin film after the third step.
Part of the thin film which deteriorates upon exposure to radiation can be removed in this step.
(10) The method of manufacturing a micro lens array may further comprise a step of removing the separation layer adhered to the surface of the thin film after the third step.
The separation layer or its residue adhered to the micro lens array can be removed in this step.
(11) The method of manufacturing a micro lens array may further comprise a step of forming shading layers which partition the thin film into predetermined areas before the second step, and the light-transmitting layer may be formed on the thin film and the shading layers in the second step.
The shading layers function as a black matrix when a micro lens array thus manufactured is incorporated into a color display device.
(12) In the method of manufacturing a micro lens array, recesses which partition the light-transmitting layer into predetermined areas may be formed on a surface of the light-transmitting layer opposite to the surface on which the lenses are formed, the recesses being filled with a shading material.
The shading material functions as a black matrix when a micro lens array thus manufactured is incorporated into a color display device.
(13) In the method of manufacturing a micro lens array, the thin film may be an alignment layer.
(14) In the method of manufacturing a micro lens array, at least one recess may be formed in the surface of the base, the recess in the base may be filled with material for the alignment layer to form a projection integrally with the alignment layer in the first step, and the projection may function as a supporting material (spacer) for maintaining a fixed space (cell gap) for sealing a liquid crystal of a liquid crystal panel (liquid crystal cell).
According to this method, the supporting material and the alignment layer can be formed at the same time, and also the location of the supporting material can be easily adjusted.
(15) The recess may be formed in an area facing an area between the lenses on the base, and the recess in the base may be placed in the area between the lenses in the second step.
This method can prevent the supporting material from being formed on the lens, thus yields can be improved and the manufacturing steps can be simplified.
(16) In the method of manufacturing a micro lens array, protrusions having shapes corresponding to alignment grooves which are to be formed on the alignment layer may be formed in a predetermined area of the surface of the base, and the alignment grooves may be formed in a predetermined area of the alignment layer in the first step.
This method can reduce the total number of steps, since the alignment grooves can be also formed on the alignment layer in the step of forming the alignment layer. The alignment grooves mean grooves that align liquid crystal molecules in a predetermined direction.
(17) In the method of manufacturing a micro lens array, the process may further comprise a step of forming a transparent electrode film on one of the alignment layer and the light-transmitting layer. The alignment layer may be provided with the light-transmitting layer through the transparent electrode film in the second step.
A micro lens array comprising the transparent electrode film can be thus easily produced.
(18) In the method of manufacturing a micro lens array, the transparent electrode film may be formed on the alignment layer.
In this manner, the transparent electrode film can be annealed separately from the light-transmitting layer, so that the light-transmitting layer is not affected by heat.
(19) A micro lens array according to the present invention is manufactured by the above-described method.
(20) A display device according to the present invention comprises the above-described micro lens array and a light source which emits light toward the micro lens array.